[gdal-dev] gdal2tiles.py generating dark tiles

[Allan Oware]

Hi all,
Dark tiles are generated when I run gdal2tiles.py on a .IMG file(a scanned
and georeferenced topographical map).
A sample png of the tiles generated is found here
<https://sites.google.com/site/lumtegis/files/519.png>. Even when i
translate to tiff, the output is still the same. Why does
gdal2tiles.py give this result ?
The gdalinfo output is as below:

Driver: HFA/Erdas Imagine Images (.img)
Files: ALOI.IMG
       ALOI.IMG.aux.xml
Size is 3830, 2552
Coordinate System is:
GEOGCS["GCS_WGS_1984",
    DATUM["WGS_1984",
        SPHEROID["WGS_1984",6378137.0,298.257223563]],
    PRIMEM["Greenwich",0.0],
    UNIT["Degree",0.017453292519943295]]
Origin = (32.999437318839924,3.000470692247897)
Pixel Size = (0.000392066994127,-0.000392066994127)
Metadata:
  DataType=Generic
Corner Coordinates:
Upper Left  (  32.9994373,   3.0004707) ( 32d59'57.97"E,  3d 0'1.69"N)
Lower Left  (  32.9994373,   1.9999157) ( 32d59'57.97"E,  1d59'59.70"N)
Upper Right (  34.5010539,   3.0004707) ( 34d30'3.79"E,  3d 0'1.69"N)
Lower Right (  34.5010539,   1.9999157) ( 34d30'3.79"E,  1d59'59.70"N)
Center      (  33.7502456,   2.5001932) ( 33d45'0.88"E,  2d30'0.70"N)
Band 1 Block=64x64 Type=UInt16, ColorInterp=Undefined
  Description = Layer_1
  Min=0.000 Max=255.000
  Minimum=0.000, Maximum=255.000, Mean=225.572, StdDev=31.338
  NoData Value=256
  Overviews: 1915x1276, 958x638, 479x319, 240x160
  Metadata:
    STATISTICS_COVARIANCES=982.046346716112,845.521289084631,710.510646703791
    STATISTICS_MINIMUM=0
    STATISTICS_MAXIMUM=255
    STATISTICS_MEAN=225.57242379015
    STATISTICS_MEDIAN=0
    STATISTICS_MODE=0
    STATISTICS_STDDEV=31.337618714831
    STATISTICS_SKIPFACTORX=1
    STATISTICS_SKIPFACTORY=1
    STATISTICS_EXCLUDEDVALUES=
    LAYER_TYPE=athematic
  Image Structure Metadata:
    COMPRESSION=RLE
Band 2 Block=64x64 Type=UInt16, ColorInterp=Undefined
  Description = Layer_2
  Min=4.000 Max=255.000
  Minimum=4.000, Maximum=255.000, Mean=226.079, StdDev=29.739
  NoData Value=256
  Overviews: 1915x1276, 958x638, 479x319, 240x160
  Metadata:
    STATISTICS_COVARIANCES=845.521289084631,884.412989496947,765.062067015664
    STATISTICS_MINIMUM=4
    STATISTICS_MAXIMUM=255
    STATISTICS_MEAN=226.07921779459
    STATISTICS_MEDIAN=0
    STATISTICS_MODE=0
    STATISTICS_STDDEV=29.739081853631
    STATISTICS_SKIPFACTORX=1
    STATISTICS_SKIPFACTORY=1
    STATISTICS_EXCLUDEDVALUES=
    LAYER_TYPE=athematic
  Image Structure Metadata:
    COMPRESSION=RLE
Band 3 Block=64x64 Type=UInt16, ColorInterp=Undefined
  Description = Layer_3
  Min=0.000 Max=255.000
  Minimum=0.000, Maximum=255.000, Mean=172.929, StdDev=27.135
  NoData Value=256
  Overviews: 1915x1276, 958x638, 479x319, 240x160
  Metadata:
    STATISTICS_COVARIANCES=710.510646703791,765.062067015664,736.335138826829
    STATISTICS_MINIMUM=0
    STATISTICS_MAXIMUM=255
    STATISTICS_MEAN=172.92884721066
    STATISTICS_MEDIAN=0
    STATISTICS_MODE=0
    STATISTICS_STDDEV=27.135495920046
    STATISTICS_SKIPFACTORX=1
    STATISTICS_SKIPFACTORY=1
    STATISTICS_EXCLUDEDVALUES=
    LAYER_TYPE=athematic
  Image Structure Metadata:
    COMPRESSION=RLE


Thanks,
Allan.
-- 
Allan Oware
Cell: +254 727 365820
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